JP4971630B2 - Phosphor, method for manufacturing the same, and light emitting device - Google Patents

Description

  The present invention includes a display such as a cathode ray tube (CRT), a field emission display (FED), a plasma display (PDP), a semiconductor light emitting element (hereinafter sometimes referred to as LED), a fluorescent lamp, a fluorescent display tube, etc. The present invention relates to a phosphor containing nitrogen and a method for producing the same used in a lighting device and a light-emitting device such as a liquid crystal backlight, and a light-emitting device including white LED lighting in which an LED and the phosphor are combined.

  Currently, discharge fluorescent lamps and incandescent bulbs used as lighting devices have various problems such as containing harmful substances such as mercury and short life. However, in recent years, high-intensity LEDs that emit light in the near ultraviolet / ultraviolet to blue have been developed one after another. From near ultraviolet / ultraviolet to blue light generated from the LEDs and phosphors having an excitation band in the garden wavelength range. Research and development is actively conducted on whether white light can be produced by mixing with the generated light, and whether the white light can be used as next-generation lighting. If this white LED lighting is put to practical use, it will not break like a conventional incandescent light bulb because it has high efficiency in converting electrical energy into light and generates less heat, and it is composed of LEDs and phosphors. There are advantages that it has a long life, does not contain harmful substances such as mercury, and that the lighting device can be miniaturized, and an ideal lighting device can be obtained.

  Even in the case of a light emitting device composed of the LED and a phosphor, an efficient device with low power consumption and high luminance is required as in a light emitting device such as a normal fluorescent lamp. In order to increase the efficiency of the device itself, it is necessary to increase the light extraction efficiency from the semiconductor element that is the excitation source, and to obtain a phosphor that efficiently converts the light that serves as the excitation source to a different wavelength. There is a demand for a phosphor that emits light efficiently with respect to light emission wavelengths of near ultraviolet, ultraviolet to blue.

For this reason, research on efficient phosphors has been actively conducted, and along with further improvements of conventional oxide, sulfide, and phosphoric acid phosphors, recently, Ca ₂ Si ₅ N ₈ : Eu, Sr ₂ Si ₅ N ₈ : Eu, Ba ₂ Si ₅ N ₈ : Eu, CaSrSi ₅ N ₈ : Eu, Ca ₂ (Al, Si) ₅ N ₈ : Ce nitride phosphors (see Patent Documents 1 and 2) ), Phosphors having new compositions such as oxynitride phosphors such as Sr ₂ Si ₃ Al ₂ N ₈ O ₂ : Eu (see Patent Document 3) have been developed one after another.

Special table 2003-515655 JP 2004-244560 A International Publication No. 2004/055910 A1 Pamphlet

  However, these phosphors according to the prior art do not have satisfactory light emission efficiency when excited by near ultraviolet / ultraviolet to green excitation light, and sufficient light emission intensity and luminance are not obtained. Furthermore, since the phosphor according to the prior art has a large decrease in light emission efficiency when the phosphor itself accumulates heat, when the phosphor is arranged around the light emitting element, the phosphor is generated by the heat generated from the light emitting element. As the luminous efficiency of the body decreases, there is a problem in that the color of the phosphor changes and the luminance decreases. In addition, the phosphor according to the prior art has a problem that the luminance is lowered when there is a heat treatment process in the air in the manufacturing process of the light emitting device. Any of these color changes and luminance reductions caused by the phosphors are obstacles to using the light-emitting device for general purposes.

  The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a phosphor excellent in luminous efficiency and luminance when excited by near ultraviolet / ultraviolet to green excitation light, and productivity. It is an object of the present invention to provide a method for manufacturing the phosphor capable of improving the brightness, and a light emitting device including white LED illumination using the phosphor. In particular, a phosphor that does not decrease in brightness or change in color even after being subjected to long-time lighting or a heat treatment in the manufacturing process, a manufacturing method thereof, and a white LED illumination using the phosphor. An object of the present invention is to provide a light-emitting device including the beginning.

  In order to solve the above-mentioned problems, the present inventors have found the cause of the brightness of the manufactured phosphor and the light emitting device being lowered and the color being changed by long-time lighting of the light emitting device and heat treatment in the manufacturing process. Pursued. As a result, the phosphors according to the prior art have insufficient resistance to oxidation, so if there is a heat treatment process in the atmosphere in the long-time lighting of the light emitting device or the manufacturing process of the light emitting device, etc. The inventors have conceived a mechanism in which oxygen contained in water, moisture in a resin or a binder, and the phosphor react with each other to cause a decrease in luminance.

Here, the present inventors formed a metal oxide film such as a SiO ₂ film on the surface of the nitride phosphor particles, thereby avoiding deterioration in the heat treatment process in the air and improving the oxidation resistance of the phosphor. I came up with a configuration to make it happen. And by the said structure, the fall of the brightness | luminance of a fluorescent substance or a light-emitting device and the change of a color by the lighting of a light-emitting device for a long time and the heat processing in a manufacturing process were able to be reduced. Furthermore, the present inventors have conducted research aimed at further reducing the luminance reduction and color change, and applied heat during the heat treatment in the manufacturing process, and heat given from the light emitting element when incorporated as a light emitting device. Oxygen atoms in a metal oxide film such as a SiO ₂ film (hereinafter sometimes simply referred to as an oxide film) covering the phosphor particles enter the inside from the surface of the phosphor particles. A new mechanism has been conceived in which the composition of the phosphor particles diffuses and the surface composition of the phosphor particles changes. Then, due to the composition change of the extreme surface, the light emission intensity and luminance of the phosphor are lowered, and as a result, a deterioration mechanism is considered that the color may change.

  Based on the above elucidation results, the present inventors consider in advance the amount of oxygen diffused from the oxide film covering the surface of the phosphor particles and accompanying the above-described degradation mechanism, and determine the amount of oxygen contained in the phosphor composition in advance. After manufacturing in a state in which the amount was less than the fixed amount, an oxide film was formed on the surface of the phosphor particles, and a heat treatment was performed at a constant temperature. Then, due to the diffusion of oxygen that occurs from the oxide film toward the phosphor particle surface after the phosphor is produced, the phosphor particles have a predetermined composition, so that a decrease in the emission intensity of the phosphor can be suppressed. In addition, preferably, the heat treatment diffuses nitrogen from the phosphor particle surface into the oxide film, thereby forming a strong oxide film on the phosphor particle surface. As a result, it has been conceived that the diffusion effect of oxygen from the atmosphere into the phosphor particles can be further suppressed by the strong shielding effect of the oxide film.

That is, the first configuration for solving the above-described problem is:
A phosphor including phosphor particles having a surface formed with a heat-treated film made of SiO ₂ ,
The composition formula of the phosphor particles is represented by a general formula MmAaBbOoNn: Z (M element is one or more elements including Sr selected from Mg, Ca, Sr, Ba, and A element is Al, Ga) One or more elements including Al selected, B element is one or more elements including Si selected from Si and Ge, O is oxygen, N is nitrogen, and Z element is Eu) and 2.5 ≦ (a + b) / m <4.5, 0 <a / m <0.5, 2.0 <b / m <4.0, 0 ≦ o / m < 1.0, o <n, and n = 2 / 3m + a + 4 / 3b-2 / 3o.

The second configuration is
The phosphor according to the first configuration,
The phosphor has a film thickness of 0.5 nm or more and 100 nm or less.

The third configuration is
The phosphor according to the first or second configuration ,
In the general formula, 2.5 <(a + b) / m <4.0, 2.5 ≦ b / m ≦ 3.5, and 0 <o / m <1.0. is there.

The fourth configuration is
The phosphor according to any one of the first to third configurations ,
The phosphor contains 0.1 wt% or more and 10.0 wt% or less of oxygen and 20.0 wt% or more and 50.0 wt% or less of nitrogen.

The fifth configuration is
The phosphor according to any one of the first to fourth configurations ,
The relative intensity value of the maximum peak in the emission spectrum at 25 ° C. when irradiating the phosphor with predetermined excitation light in the wavelength range of 250 nm to 500 nm is BP,
When the phosphor is placed in an atmosphere of 300 ° C. for 6 hours, then returned to 25 ° C., and the value of the relative intensity of the maximum peak in the emission spectrum when irradiated with the excitation light is AP,
The phosphor is characterized in that (BP-AP) /BP≦0.05.

The sixth configuration is
A phosphor placing serial to any of the fifth configuration from the first,
The phosphor has an average particle diameter (D50) of 1.0 μm or more and 20 μm or less.

The seventh configuration is
A method for producing the phosphor according to any one of the first to sixth configurations ,
A step of firing phosphor materials to obtain phosphor particles;
Crushing the phosphor particles;
In a water-soluble organic solvent, the pulverized phosphor particles, the organosilane compound, and water are added and mixed, and then a gelling agent is added to form a film containing a metal oxide on the surface. Obtaining phosphor particles having,
Phosphor particles having a coating containing the metal oxide on the surface thereof are heat-treated in an atmosphere of ammonia gas and / or nitrogen gas at 1000 ° C. or lower and 200 ° C. or higher to obtain a heat-treated coating containing the metal oxide. And a step of producing the phosphor particles having the phosphor.

The eighth configuration is
A light emitting device comprising the phosphor according to any one of the first to sixth configurations and a light emitting unit.

The ninth configuration is
A light-emitting device according to an eighth configuration ,
The light emitting unit is a light emitting device that emits light in any wavelength range of 250 nm to 500 nm.

The tenth configuration is
The light-emitting device according to the eighth or ninth configuration ,
An LED (light emitting diode) is used as the light emitting unit.

In the phosphor described in any one of the first to sixth configurations, the surface of the phosphor particles is coated with a dense oxide that has been subjected to heat treatment. Alteration can be avoided and oxygen and moisture from the outside can be blocked. For this reason, it is possible to suppress a decrease in light emission characteristics due to a change in composition caused by heat applied during lighting or heat treatment.

According to the phosphor manufacturing method according to the seventh configuration , a phosphor including phosphor particles having a heat-treated metal oxide film on the surface can be easily manufactured with high productivity.

The light-emitting device described in any one of the eighth to tenth configurations has excellent durability, and there is no significant decrease in luminance in human vision even when used for a long time, or a remarkable light color. It is an excellent light-emitting device that does not feel change.

Hereinafter, embodiments of the present invention will be described in detail.
First, the brightness of phosphor particles having an oxide film on the surface by heat generated by a long-time lighting in a light-emitting device in which the phosphor is installed or heat by heat treatment in the phosphor manufacturing process, which has been elucidated by the present inventors. Deterioration mechanism that lowers will be described.

Initially, the present inventors considered to suppress the temperature rise of the phosphor surface that causes a degradation mechanism of the phosphor during light emission of the light emitting device in which the phosphor is installed. And, in order to suppress the temperature rise, by providing an oxide film with low thermal conductivity on the phosphor particle surface containing nitrogen, it is possible to avoid alteration of the phosphor particles due to the temperature rise of the surface, and external It was conceived that oxygen supply to the inside of the phosphor particles could be cut off from the inside. In particular, it was conceived that by providing a SiO ₂ oxide film as an oxide, alteration of the phosphor particle surface due to temperature rise can be easily avoided. Moreover, even if the oxide film is other than SiO ₂ , it has been conceived that the same effect can be obtained by using ZrO ₂ , TiO ₂ or the like. When an oxide of In or Sn is used as the oxide film, since the oxide film also has conductivity, electrons are directly irradiated on the phosphor surface like a phosphor used in a display or the like. It can be said that it is a preferable conductive oxide film for use.

However, according to further studies by the present inventors, even if an oxide film is provided on the surface of the phosphor particles as described above, the light emission characteristics of the phosphor deteriorated over a long period of time when the temperature rose.
This is because the temperature of the phosphor applied on the surface of the light emitting element or in the vicinity of the light emitting element rises to about 200 ° C., for example, due to heat generated from the light emitting element in the light emitting device provided with the phosphor. In addition, in the manufacturing process of the light emitting device, it is considered that the temperature of the phosphor particles is also increased when the light emitting element is subjected to heat treatment. A phosphor having an oxide film on a surface that was relatively stable at room temperature (25 ° C.) increases the temperature of the surface of the phosphor particles due to heat applied during lighting and heat treatment for a long time. Oxygen atoms in the coated oxide film enter and diffuse from the phosphor surface to the inside. Furthermore, oxygen in the air or resin, moisture in the binder containing organic matter, etc. penetrates and diffuses into the phosphor particles through the oxide film, so that the surface composition of the phosphor particles changes and the phosphor This has led to a deterioration mechanism in which the light emission intensity and brightness of the light source are reduced.

  Here, the heat treatment in the manufacturing process of the light emitting device means that the phosphor is mixed with various binders such as a resin that is an organic material and applied to the light emitting element or the like in order to attach the phosphor to the light emitting element or the like. The heat treatment is performed to cure or evaporate the binder. Although various conditions can be considered as the heat treatment conditions depending on the resin or organic substance to be used, the conditions are such that the temperature is maintained at about 100 ° C. for several hours. Therefore, it is considered that the heat-resistant deterioration performance required for the phosphor is not sufficient to evaluate the rate of decrease in emission intensity after being kept in the atmosphere at 100 ° C. for several hours. Then, considering that the temperature of the light emitting element rises to about 200 ° C. and whether or not the phosphor has sufficient durability as a member, the phosphor is heated to 300 ° C. at 6 ° C. It was considered necessary to evaluate the rate of decrease in emission intensity after being kept in the atmosphere for a period of time. And in the said evaluation, if the value of the decreasing rate of emitted light intensity is small, it can be said that it is a preferable fluorescent substance excellent in durability.

  Here, in order to prevent a decrease in luminous efficiency due to diffusion of oxygen from the oxide film itself to the phosphor particles, which causes the phosphor degradation mechanism, the present inventors apply the phosphor surface to the oxide film as described above. In addition to the structure coated with, an oxygen atom that diffuses from the oxide film to the phosphor particles is absorbed into the phosphor composition, resulting in a harmless structure. That is, the present inventors pay attention to the abundance of Si and Al in the phosphor composition, and after replacing a part of Si atoms contained in the phosphor with Al atoms in advance, the oxide film It is conceived that the structure is covered with heat treatment and heat-treated.

  That is, in consideration of the amount of oxygen diffused from the oxide film covering the phosphor surface to the phosphor particles, by adding a predetermined amount of Al in advance during the creation of the phosphor, Si atoms in the phosphor particles A part of this is substituted with Al atoms to produce phosphor particles in a state where oxygen is deficient. Next, an oxide film is formed on the surface of the phosphor particles in which oxygen is deficient, and heat treatment is further performed. Then, diffusion of oxygen from the oxide film toward the phosphor particles occurs, but the diffused oxygen is consumed to eliminate the oxygen deficiency, and a decrease in the emission intensity of the phosphor can be avoided. it is conceivable that.

  On the other hand, by the heat treatment described above, nitrogen atoms in the phosphor particles diffuse from the inside of the phosphor particles into the oxide film that is a coating. Nitrogen diffused in the oxide film is considered to react with a metal that has lost oxygen in the oxide film to form a metal nitride. Here, in general, since metal nitride is a dense and mechanically strong film, diffusion of oxygen entering the atmosphere from the atmosphere through the oxide film due to the formation of metal nitride in the oxide film. Exhibits a preferable effect of suppressing the above.

  Further, it is preferable that the phosphor particles are heat-treated at a temperature of 1000 ° C. or lower and 200 ° C. or higher in an atmosphere of ammonia gas and / or nitrogen gas, and the phosphor particles and the oxide film thereof are heat-treated. is there. Also in the case of the heat treatment in the atmosphere, diffusion of nitrogen occurs on the surface of the oxide film and metal nitride is generated, so that a stronger and denser oxide film is formed. As a result, from the atmosphere through the oxide film, It exhibits a preferable effect of suppressing the diffusion of oxygen entering the inside.

  The composition of the phosphor particles to which the present invention is applied is not particularly limited, and can be applied to phosphors containing various phosphor particles. However, the present invention is particularly effective for phosphor particles containing nitrogen that have problems such as deterioration of the phosphor surface, reduction in luminance, and change in color due to long-time lighting. . Here, the particle shape of the phosphor may be spherical, plate-shaped, or columnar, and is not particularly limited.

  The composition formula of the phosphor particles containing nitrogen to which the present invention is particularly effectively applied is represented by MmAaBbOoNn: Z, where the M element is an element having a valence of II, and the A element is a valence of III. B element is an element having IV valence, O is oxygen, N is nitrogen, Z element is an activator and is selected from rare earth elements and transition metal elements Element.

The present invention can be suitably applied to any phosphor containing nitrogen in which n> 0 in the relationship of m, a, b, o, and n in the composition formula.
For example, a phosphor represented by the general formula MmAaBbOoNn: Z (M element is one or more elements having a valence of II and A element is one or more elements having a valence of III B element is one or more elements having an IV valence, O is oxygen, N is nitrogen, and Z element is one or more activators.), 2.5 ≦ (a + b) / m <4.5, 0 <a / m <0.5, 2.0 <b / m <4.0, 0 ≤ o / m <1.0, o <n, n = 2 / 3m + a + 4 / 3b- There is a phosphor that is 2 / 3o.

  Here, the M element, the A element, the B element, and the Z element contained in the phosphor particles according to the above-described embodiment will be further described.

  The M element is one or more elements having a valence of II, but preferably one or more elements selected from Mg, Ca, Sr, Ba, and Zn.

  The element A is one or more elements having a valence of III, but is preferably one or more elements selected from Al and Ga.

  The element B is one or more elements having a valence of IV, preferably one or more elements selected from Si and Ge.

  The Z element is at least one element selected from rare earth elements or transition metal elements that act as activators, but is preferably one or more elements selected from Eu, Ce, and Mn.

  When the element Z contains Eu, the phosphor has a good excitation band for light in the wavelength range from near ultraviolet / ultraviolet to visible light (250 nm to 550 nm), and red (580 nm to 680 nm). It becomes the fluorescent substance excellent in light emission which has a broad peak in the range.

  For these preferable elements listed as M element, A element, B element, and Z element, by selecting these elements, not only a phosphor with excellent characteristics can be obtained, but also the acquisition of raw materials is easy, There is also an advantage that the environmental load is small.

  Further, the phosphor represented by the general formula MmAaBbOoNn: Z, which is 2.5 ≦ (a + b) / m <4.5, 0 <a / m <0.5, 2.0 <b / m <4.0, 0 ≦ In the phosphor where o / m <1.0, o <n, n = 2 / 3m + a + 4 / 3b-2 / 3o, oxygen is contained in an amount of 1.0 wt% or more and 10.0 wt% or less, and nitrogen is further contained. Containing 20.0wt% or more and 50.0wt% or less.

  In particular, in the general formula described above, 2.5 <(a + b) / m <4.0, 0 <a / m <0.5, 2.5 ≦ b / m ≦ 3.5, 0 <o / m <1.0, Although the phosphor particles using the phosphor have excellent light emission characteristics, they have a problem that they are very weak against heat, so that the effect obtained by applying the present invention is great. This is because, in phosphor particles containing Sr as a constituent element, Sr easily elutes into moisture, so that the phosphor surface can be easily altered or the crystal structure is destroyed due to external factors such as heat and moisture. In addition, the light emission characteristics of the phosphor are greatly deteriorated. Here, by applying the present invention to the phosphor, the external factors causing the phosphor modification can be suppressed by the metal oxide film, so that the phosphor modification can be avoided. Furthermore, since the phosphor particles and the metal oxide coating are subjected to heat treatment, defects and distortions on the surface of the phosphor particles generated in the crushing process and the like are removed. It is considered that the collapse of the structure can be suppressed and the decrease in luminance and the change in color of the phosphor can be improved.

  In the phosphor of this embodiment, the amount of Z element added is preferably in the range of 0.0001 mol or more and 0.5 mol or less with respect to 1 mol of the corresponding M element. When the amount of Z element added is in this range, it is possible to avoid concentration quenching due to the presence of an excessive activator and reduction in luminous efficiency due to an excessive amount. Depending on the element to be added and the structure of the matrix (difference in composition formula), the optimum amount of addition of Z element is slightly different, but more preferably in the range of 0.005 mol or more and 0.2 mol or less.

The present invention is not limited to phosphors having the above-described composition formula, but also known phosphor compositions such as Ca ₂ Si ₅ N ₈ : Eu, CaSrSi ₅ N ₈ : Eu, Sr ₂ Si ₅ N ₈ : Eu, etc. It can also be applied to a silicon nitride fluorescent system.

(Method for producing phosphor according to the present invention)
Here, with respect to the method for producing a phosphor according to the present invention, the Sr ₄ AlSi ₁₁ (O ₂ ) N ₁₇ : Eu in which the M element is suitably applied to the present invention is Sr, the B element is Si, and the Z element is Eu. The production of a phosphor in which a SiO ₂ film is formed on phosphor particles having the composition (Eu / (Sr + Eu) = 0.030) will be described as an example. However, Sr ₄ AlSi ₁₁ (O ₂ ) N ₁₇ : Eu, which is the composition, is a composition formula in which the value calculated from the raw material mixture ratio is expressed using the general formula MmAaBbOoNn: Zz. Therefore, even if the composition ratio of the manufactured phosphor is shifted within a range of about 5% from the composition ratio of the composition formula, a phosphor having sufficiently practical characteristics can be obtained. In particular, the oxygen concentration in the composition formula is adjusted according to the manufacturing method described later, and thus is not necessarily as described above. Eu / (Sr + Eu) means z / (m + z).

  In general, many phosphors are produced by a solid-phase reaction, and the method for producing the phosphor of this embodiment can also be obtained by a solid-phase reaction. However, the manufacturing method is not limited to these. The raw materials for M element, A element, and B element may be commercially available raw materials such as nitrides, oxides, carbonates, hydroxides, basic carbonates, etc., but carbonates are particularly preferable for M elements. Since it is preferable that the purity is higher, a material having a purity of 2N or more, more preferably 3N or more is prepared. In general, the particle diameter of each raw material particle is preferably a fine particle from the viewpoint of promoting the reaction, but the particle diameter and shape of the obtained phosphor also vary depending on the particle diameter and shape of the raw material. For this reason, a powdery raw material such as a nitride having an approximate particle size may be prepared in accordance with the particle size and shape required for the finally obtained phosphor. As for the element Z, commercially available nitrides, oxides, carbonates, hydroxides, basic carbonates, or simple metals can also be used as raw materials. Of course, the purity of each raw material is preferably higher, and 2N or more, more preferably 3N or more is prepared. In particular, when carbonate is used as the raw material for the M element, the flux effect can be obtained without adding a compound containing an element not included in the constituent elements of the phosphor of the present embodiment as a flux (reaction accelerator). This is a preferable configuration because it can be obtained.

In the production of the composition formula Sr ₄ AlSi ₁₁ (O ₂ ) N ₁₇ : Eu (where Eu / (Sr + Eu) = 0.030), for example, SrCO ₃ ( 3N), AlN (3N), and Si ₃ N ₄ (3N) are prepared, and Eu ₂ O ₃ (3N) is preferably prepared as the Z element. In these raw materials, the mixing ratio of each raw material was 0.970 mol for SrCO ₃ and 0.25 mol for AlN so that the molar ratio of each element would be Sr: Al: Si: Eu = 0.970: 0.25: 2.75: 0.030. Then, weigh 2.75 / 3 mol of Si ₃ N ₄ and 0.030 / 2 mol of Eu ₂ O ₃ and mix them. The reason why carbonate is used as the Sr raw material is that when a low melting point raw material such as carbonate is used, the raw material itself acts as a flux, the reaction is promoted, and the light emission characteristics are improved.

  In addition, when an oxide is used as a raw material, another substance may be added as a flux in order to obtain a flux effect. In this case, the flux may become an impurity, which may deteriorate the characteristics of the phosphor. Note that there is. The weighing and mixing are preferably performed in the glove box under an inert atmosphere from which moisture has been sufficiently removed because the nitrides of the respective raw material elements are easily affected by moisture, but may be performed in the air. Either a wet method or a dry method may be used, but if pure water is used as a solvent for wet mixing, the nitride raw material is oxidized, and therefore an appropriate organic solvent must be selected. The apparatus may be a normal apparatus using a ball mill or a mortar.

  The mixed raw material is put into a crucible and may contain inert gas such as rare gas, reducing gas such as hydrogen and ammonia, but 1600 ° C or higher in a gas atmosphere containing 90% or more of nitrogen gas. Preferably, baking is performed at 1700 ° C. or more and 2000 ° C. or less for 30 minutes or more. When the firing temperature is 1600 ° C. or higher, it is possible to obtain a phosphor excellent in light emission characteristics through favorable solid-phase reaction. Further, if firing at 2000 ° C. or less, excessive sintering and melting can be prevented. In addition, since a solid-phase reaction advances rapidly, so that a calcination temperature is high, holding time can be shortened. On the other hand, even when the firing temperature is low, the desired light emission characteristics can be obtained by maintaining the temperature for a long time. However, the longer the firing time, the more the particle growth proceeds and the larger the particle shape. Therefore, the firing time may be set according to the target particle size.

The furnace pressure during the firing is preferably 0.5 MPa or less, more preferably 0.1 MPa or less. (In this embodiment, the furnace pressure means the amount of pressure from atmospheric pressure.) This avoids excessive sintering between particles by firing at a pressure of 0.5 MPa or less. This is because pulverization after firing can be facilitated. In addition, as the crucible, those that can be used in the above gas atmosphere such as Al ₂ O ₃ crucible, Si ₃ N ₄ crucible, AlN crucible, sialon crucible, C (carbon) crucible, BN (boron nitride) crucible are used. However, it is preferable to use a BN crucible because it can avoid contamination of impurities from the crucible.

  Further, during firing, it is preferable to perform firing in a state where the above gas atmosphere is flowed at a flow rate of, for example, 0.1 ml / min or more. This is because gas is generated from the raw material during firing, but by flowing a gas atmosphere containing 90% or more of the nitrogen gas described above, the gas generated from the raw material fills the furnace and affects the reaction. This is because it is possible to prevent deterioration of the light emission characteristics of the phosphor. In particular, when carbonates, hydroxides, and basic carbonates are used as raw materials, gas is generated when the raw materials decompose and become oxides during firing, so the atmosphere in the firing furnace flows, It is preferable to exhaust the generated gas.

In the present embodiment, it is preferable to fire the raw material as powder. In a general solid phase reaction, in consideration of the progress of the reaction due to the diffusion of atoms at the contact between the raw materials, the raw materials are often baked in the form of pellets in order to promote a uniform reaction throughout the raw materials. However, in the case of the phosphor raw material, it is easy to handle as a powder because it is easy to disintegrate after firing by firing it as powder and the primary particles have an ideal spherical shape. This is preferable. In addition, when carbonates, hydroxides, or basic carbonates are used as raw materials, CO ₂ gas and the like are generated by decomposition of the raw materials during firing. Therefore, the raw material is preferably a powder from the viewpoint of not adversely affecting the light emission characteristics. In addition, in the phosphor of the present embodiment, particles having a columnar particle shape are observed in the phosphor particles as the light emission characteristics are improved. This is because in the composition of the phosphor of the present embodiment, it is easy to take a columnar particle shape when crystal growth proceeds, and the particle having the columnar particle shape exhibits excellent light emission characteristics. Conceivable. Therefore, from the viewpoint of improving the light emission characteristics, the primary particles of the phosphor preferably include columnar particles.

  As a method for adjusting the composition of this phosphor, Al may be weighed by a few percent at the time of mixing the raw materials, but it is easier to change the oxygen concentration by adjustment at the time of firing. The method for adjusting the oxygen concentration may be adjusted according to the firing temperature, firing time, or atmospheric flow rate although the production conditions differ depending on the furnace for firing the phosphor (for example, a batch furnace, a continuous furnace, or a pressure furnace). If the firing temperature is increased, the firing time is lengthened, or the atmospheric flow rate during firing is increased, the oxygen concentration after generation is lowered. The target oxygen concentration may be a numerical value suitable for the amount of oxygen diffusing inside depending on the thickness of the oxide film to be coated, the heat treatment temperature after generation, and the time. In general, the thickness of the oxide is 0.5 nm or more and 100 nm or less, and the volume ratio of the oxide film to the fluorescent particles is several percent or less. What is necessary is just to set it as the oxygen amount reduced by 1% to 2% from the oxygen amount calculated | required from a type | formula.

After the firing is completed, the fired product is taken out from the crucible, and ground using a mortar, ball mill, or other pulverizing means so as to have a predetermined average particle size, and the composition formula Sr ₄ AlSi ₁₁ (O ₂ ) N ₁₇ : Eu (However, Eu / (Sr + Eu) = 0.030) can be produced. Thereafter, the obtained phosphor is washed, classified, and surface-treated as necessary.
When other elements are used as M element, A element, B element, and Z element, and when the activation amount of Eu as an activator is changed, the blending amount at the time of charging each raw material is set to a predetermined value. By adjusting to the composition ratio, the phosphor can be manufactured by the same manufacturing method as described above.

Next, the crushing process of the phosphor particles will be described.
The phosphor particles after firing are crushed using a mortar, ball mill, jet mill, sample mill, roller mill or the like. For the reasons described later, it is preferable to perform the crushing so that the average particle diameter of the phosphor particles is 1.0 μm or more and 20 μm or less.

Next, a process for coating the surface of the phosphor particles with an oxide film will be described. As the oxide film, an oxide film composed of Si, Ti, Zr, In, and Sn is preferable. However, providing an SiO ₂ film is preferable because it is inexpensive and easy to manufacture. However, similar effects can be obtained even in the oxide film of ZrO _2, TiO _2, etc. In addition SiO _2. In addition, when an oxide film of In or Sn is used, the oxide film has conductivity in addition to covering the phosphor surface, so that it is preferable in applications where electrons are directly irradiated on the phosphor surface, such as for displays. It can be said that it is an oxide film.

A so-called sol-gel method is preferred as a method of coating the surface of the phosphor particles with an oxide film such as a SiO ₂ film. The sol-gel method is a method in which a hydrolysis product of a coating substance is first deposited on the surface of phosphor particles, and then the hydrolysis product is subjected to a condensation reaction with a catalyst or the like. Therefore, in the case of the present embodiment, the coating of the SiO ₂ film on the phosphor particles starts by mixing phosphor particles, an organosilane compound, and water in an organic solvent and performing a sol hydrolysis reaction.

  Here, the organic solvent is preferably water-soluble in order to function as a sol medium for proceeding the hydrolysis reaction, and particularly alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol are preferable.

As the organosilane, an alkoxysilane represented by the general formula R1 _4-a Si (OR2) _a (where R1 is a monovalent hydrocarbon group, R2 is a monovalent hydrocarbon group having 1 to 4 carbon atoms, a Is an integer of 3 to 4.) Among them, tetraethoxysilane (hereinafter referred to as TEOS) and methyltrimethoxysilane are preferable.

In order to hydrolyze the alkoxysilane on the surface of the phosphor particles, pure water to be subjected to hydrolysis and the phosphor particles are put in the organic solvent and stirred, and the phosphor particles are suspended. deep. Next, alkoxysilane is added to the suspension and stirred. Thereafter, a catalyst for promoting the hydrolysis / condensation reaction is added and stirred. As a result, a coating film containing SiO ₂ gel is formed on the surface of the phosphor particles.

As a gelling agent for promoting the hydrolysis / condensation reaction, an acid such as hydrochloric acid, sulfuric acid or phosphoric acid may be used, but from the viewpoint of obtaining a uniform and dense SiO ₂ film, an alkali is preferable. Ammonia without metal content is preferred. In addition, by using ammonia, a uniform and dense SiO ₂ film can be obtained satisfactorily, and there are many advantages such as easy availability and low cost, easy volatilization removal, and no residual impurities.

  Here, as the reaction tank used for the hydrolysis reaction, it is preferable to use a ceramic reaction tank, a Teflon (registered trademark) -coated reaction tank, or the like, rather than a metal tank. This is because when stirring in an organic solvent, the stirring blade and the reaction vessel wall are scraped off by collision with the phosphor particles, and may be mixed into the phosphor powder as an impurity that lowers the emission intensity. . In particular, the concentration of Fe, Ni, Co element in the phosphor is preferably 100 ppm or less.

It is desirable that the hydrolysis reaction and the subsequent condensation reaction proceed by aging after adding aqueous ammonia. The addition rate of the ammonia water is not particularly limited, but by slowly adding it, the pH of the phosphor suspension is avoided at once, and the structure of the oxide film such as SiO ₂ film coated on the phosphor particles is reduced. It can avoid becoming coarse.

Moreover, when adding ammonia water, aggregation of the fluorescent substance particles coated can be prevented by adding continuously. This is because by adding ammonia water continuously and gradually raising the pH of the phosphor suspension, SiO ₂ particles are generated in the suspension other than the phosphor particle surface, and the SiO ₂ particles are fluorescent. This is because the situation of acting as a binder that induces aggregation of body particles can be avoided. Furthermore, by gradually increasing the pH of the phosphor suspension, the surface of the phosphor particles is unevenly formed due to non-uniform generation of SiO ₂ , and the phosphor particles tend to aggregate. Can be avoided. Moreover, the liquid temperature at the time of aging after completion of the addition of ammonia water is not particularly limited, but is preferably 10 ° C to 70 ° C, and more preferably about 40 ° C. When the liquid temperature is about 10 ° C. to 70 ° C. or about 40 ° C., it can be avoided that the oxide film such as the SiO ₂ film becomes rough. The aging time is not particularly limited, but is preferably 0.5 hr to 5 hr.

The film thickness and film density of the SiO ₂ film on the phosphor particles obtained by the above operations generally depend on the initial alkoxysilane amount, pure water amount, phosphor suspension liquid temperature, aging time, and the like. Therefore, by controlling the amount of alkoxysilane and the like, a SiO ₂ gel film having an arbitrary film thickness and film density can be deposited on the phosphor particle surface. By setting the thickness of the SiO ₂ gel coating film to 400 nm or less, preferably 100 nm or less, and more preferably less than 20 nm, the coated phosphor particles can be prevented from aggregating with each other.

Next, control of the film thickness of the SiO ₂ gel coating film by adjusting the amount of added alkoxysilane will be described.

First, the amount of alkoxysilane to be added is (W1), the target SiO ₂ gel coating film thickness is (L), the specific surface area of the phosphor particles determined by the BET method is (S), and the phosphor particles are charged. Let the amount be (W3). Then, when the surface of all the added phosphor particles (S × W3) is coated with SiO ₂ gel with film thickness (L), the volume (V1) of SiO ₂ gel coating is
V1 = S × W3 × L ... (Formula 1)
It becomes.

On the other hand, assuming that the density of the SiO ₂ gel coating is ρ (silica gel = 2.0 g / cm ³ equivalent), the weight (W2) of SiO ₂ generated on the surface of all phosphor particles is
W2 = V1 × ρ… (Formula 2)
It becomes.

Therefore, when the molecular weight of SiO ₂ is (Mw2) and the molar amount of SiO ₂ is (M1), the molar amount of the SiO ₂ film generated on the surface of all phosphor particles is
M1 = W2 / Mw2 ... (Formula 3)
It becomes.

In the case of alkoxysilanes, for example _{TEOS, Si (OC 2 H 5} ) 4 in 1.0 mol, since Si is present 1.0 mol, SiO ₂ generated from _{Si (OC 2 H 5) 4} 1.0mol Is 1.0 mol. That is, since M1 mol of TEOS is also required to generate M1 mol of SiO ₂ , when the molecular weight of TEOS is (Mw1), the amount of alkoxysilane (W1) is
W1 = M1 × Mw1 ... (Formula 4)
It becomes.

And from Formula 1 to Formula 4,
W1 = S x W3 x L x rho x Mw1 / Mw2 (Formula 5)
Since ρ, Mw1, and Mw2 are constants, S is a measured value, and W3 is a predetermined set value, if the desired film thickness value L is substituted into Equation 5, the amount of alkoxysilane to be added (W1 ).

Further, when Equation 5 is solved for the film thickness value L,
L = [Mw2 / (S × W3 × ρ × Mw1)] × W1 (Formula 6)
The coating film thickness value (L) of the SiO ₂ gel can be calculated from the amount of added alkoxysilane (W1).

Furthermore, as an example of a method for directly obtaining the coating film thickness value (L) of the SiO ₂ gel, it can be obtained from the result of high-magnification observation using a transmission electron microscope (TEM).

The obtained phosphor particles coated with the SiO ₂ gel film are isolated from the phosphor suspension by solid / liquid separation. Filtration is common as a method for solid / liquid separation. The drying method may be a general method such as warm air drying, vacuum drying, or spray dryer.

Next, the process of heat-treating the phosphor particles will be described.
As a condition for the heat treatment, the heat treatment temperature needs to be set to a temperature at which particles are not sintered and a temperature at which a stable phase can be formed which is stable even at a temperature exposed when the phosphor is incorporated into a product. . The heat treatment temperature is preferably 1600 ° C. or lower, more preferably 1000 ° C. or lower, more preferably 500 ° C. or lower, and 200 ° C. or higher. The heat treatment time varies depending on the heat treatment temperature, but is preferably 0.5 hours or longer.

  As the heat treatment atmosphere, when the phosphor surface is oxidized, the surface structure is changed to a structure not suitable for light emission. Therefore, it is preferable to perform in an atmosphere gas containing nitrogen as a constituent element and not containing oxygen. A mixed gas atmosphere of ammonia gas, nitrogen gas, ammonia gas and nitrogen gas is preferable. In addition, when using ammonia gas atmosphere, since ammonia is corrosive gas, it is necessary to use the furnace whose furnace material is not corroded by ammonia. In addition, although there is a slight possibility that gas may be generated from the phosphor particles subjected to the heat treatment, it is preferable to circulate the atmospheric gas. By the heat treatment, phosphor particles having excellent durability can be obtained by diffusion of oxygen from the surface oxide film to the phosphor particles and diffusion of nitrogen from the phosphor particles to the surface oxide film.

The thus obtained heat-treated SiO ₂ film on the surface, and the phosphor particles that have been heat-treated themselves, compared with untreated phosphor particles, are heat-degraded, resulting in lower brightness and color due to prolonged lighting. Taste change is suppressed.

As a result, the relative intensity of the maximum peak in the emission spectrum at 25 ° C. of the phosphor irradiated with predetermined excitation light in the wavelength range of 250 nm to 500 nm is BP, and the phosphor is 300 It was kept in the atmosphere at ℃ for 6 hours and thermally deteriorated, then returned to 25 ℃, and the relative intensity of the maximum peak in the emission spectrum when irradiated with the predetermined excitation light was defined as the emission intensity as AP. When a phosphor containing phosphor particles provided with a heat-treated SiO ₂ film on its surface, the rate of change with respect to the thermal degradation is (BP−AP) /BP≦0.05, which is excellent in heat resistance It has been found.

In the present embodiment, when the heat-treated SiO ₂ coating is provided and the phosphor containing the heat-treated phosphor particles is used in the form of powder, the average particle diameter of the powder of the phosphor Is preferably 20 μm or less. This is because light emission is considered to occur mainly on the particle surface in the phosphor, and if the average particle size is 20 μm or less, a surface area per unit weight of the powder can be secured and a reduction in luminance can be avoided. . Furthermore, when the powder is applied as a paste to a light emitting element or the like, the application density can be increased, and from this point of view, a reduction in luminance can be avoided. Usually, when SiO ₂ is coated on the particle surface by hydrolysis and polymerization, the particles tend to aggregate, and the average particle diameter after coating is often greatly increased compared to the average particle diameter before coating. However, according to the manufacturing method of this embodiment described above, aggregation is hardly observed, and the average particle diameters before and after coating are substantially equal. Further, even when heat treatment is performed after coating, since the treatment temperature is low, aggregation is hardly observed. That is, if the average particle diameter of the phosphor powder before coating is 20 μm or less and the production method of this embodiment is applied, the phosphor having an average particle diameter of 20 μm or less can be easily obtained. is there. Further, according to the study by the present inventors, although the detailed reason is unknown, it was also found that the average particle diameter of the phosphor powder is preferably larger than 1 μm from the viewpoint of the luminous efficiency of the phosphor powder. . From the above, the average particle size of the phosphor powder of the present embodiment is preferably 1 μm to 20 μm.

  By combining the phosphor of the present embodiment in powder form with a light emitting part that emits light in a wavelength range of 250 nm to 550 nm, preferably in a wavelength range of 250 nm to 500 nm, A light emitting device such as a display backlight device can be manufactured.

  As the light emitting unit, for example, an LED light emitting element that emits light in a range from ultraviolet to blue, a discharge lamp that generates ultraviolet light, and the like can be used. And when the mixture which mixed the fluorescent substance of this embodiment, and another fluorescent substance is combined with the said LED light emitting element, light-emitting devices, such as various illuminating devices and a backlight apparatus for a display, can be manufactured. . In addition, even when a mixture obtained by mixing the phosphor of this embodiment and another phosphor is combined with the discharge lamp, it is possible to manufacture various light emitting devices such as various fluorescent lamps, illumination devices, and display backlight devices. it can.

  A combination method of the phosphor of this embodiment and the LED light emitting element or the Hg discharge lamp may be performed by a known method. For example, a method in which the phosphor is directly applied to the light emitting part, a method in which the phosphor is dispersed in a resin such as silicon, and then a dispersion is applied to the light emitting part. It can apply | coat to a base material etc. and the method of arrange | positioning the said base material on the light emission part upper part can be taken.

  In the above-described light emitting device, when an LED light emitting element, an Hg discharge lamp, or the like emits light, these light emitting portions emit light of a predetermined wavelength, and part or all of the light of the predetermined wavelength serves as an excitation source, and the fluorescent light It is possible to obtain a light emitting device such as white light whose body emits light at a wavelength different from the predetermined wavelength and has excellent durability and luminance.

Hereinafter, based on an Example, this invention is demonstrated more concretely.
Example 1
In Example 1, the composition formula is SrAl _0.2 Si _2.7 (O) N _3.80 : Eu (where Eu / (Sr + Eu) = 0.030), and a heat-treated SiO ₂ film is provided on the surface, In addition, a phosphor containing phosphor particles that had been heat-treated was manufactured. As a manufacturing method, M element, A element, as the raw material of the element B, respectively commercially available _{SrCO 3 (3N), AlN (} 3N), to prepare a Si ₃ N ₄ (3N), as the element Z, Eu ₂ O Prepare ₃ (3N). The mixing ratio of each raw material is 0.970 mol for SrCO ₃ and 0.20 mol for AlN so that the molar ratio of each element is Sr: Al: Si: Eu = 0.970: 0.20: 2.70: 0.030. Then, 2.70 / 3 mol of Si ₃ N ₄ and 0.030 / 2 mol of Eu ₂ O ₃ were weighed and mixed in the atmosphere using a rotating ball mill. Put the mixed raw materials in a BN crucible, raise the temperature to 1600 ° C at 15 ° C / min in a nitrogen atmosphere (flow state) at 0.05 MPa, hold and fire at 1600 ° C for 6 hours, and then from 1600 ° C to 200 ° C Cooled in 1 hour. After that, the fired sample is mixed and pulverized in the air, and the mixed and crushed sample is put again in the crucible, and the temperature is increased to 1750 ° C at a furnace pressure of 0.05 MPa at 15 ° C / min in a nitrogen atmosphere (flow state). After heating and holding at 1750 ° C. for 12 hours and main firing, it was cooled from 1750 ° C. to 200 ° C. in 1 hour. Thereafter, the fired sample is mixed and pulverized in a mortar until the particle size becomes an appropriate particle size in the atmosphere, and the composition formula SrAl _0.2 Si _2.7 (O) N _3.80 : Eu (however, Eu / (Sr + Eu) = 0.030) was obtained.

30 g of the obtained phosphor sample was put into a mixed solvent of 500 g of isopropyl alcohol and 62.2 g of pure water, the liquid temperature was kept at 40 ° C., and stirring was continued, so that the film thickness became 5.0 nm. 0.541 g of tetraethoxysilane (TEOS, 95%) obtained from Formula 5 was added. After the addition of TEOS, 111.5 g of aqueous ammonia (21.83%) was continuously added over 45 min, and further aging was continued for 60 min. After separating the phosphor powder from the obtained reaction solution by filtration, the phosphor powder was dried at 100 ° C. for 3 hours or more to obtain a phosphor powder having a SiO ₂ film.

Next, phosphor powder having an SiO ₂ film was filled in a BN crucible, heated to 300 ° C. at 10 ° C./min in an ammonia atmosphere, and kept at 300 ° C. for 3 hours for heat treatment. In this way, a heat-treated SiO ₂ film was provided on the surface, and phosphor particles that were also heat-treated were obtained. The obtained phosphor particles had an oxygen concentration of 3.74 wt% and an average particle size (D50) of 12.08 μm.

(Comparative Example 1)
In Comparative Example 1, a phosphor powder containing the phosphor particles was obtained by performing the same treatment as in Example 1 except that the phosphor particles and the SiO ₂ film formed thereon were not subjected to heat treatment. A 5 nm SiO ₂ film was formed on the phosphor particle surface, but heat treatment in ammonia was not performed. The phosphor powder thus produced had an oxygen concentration of 3.64 wt% and an average particle size (D50) of 12.13 μm.

(Example 2)
In Example 2, phosphor particles are produced by the same composition ratio and production method as in Example 1, and 30 g of the obtained phosphor particles are put into a mixed solvent of 500 g of isopropyl alcohol and 62.2 g of pure water. While maintaining the liquid temperature at 40 ° C. and continuing stirring, 2.020 g of tetraethoxysilane (TEOS, 95%) obtained from the above formula 5 was added so that the film thickness was 20.0 nm. After the addition of TEOS, 443.0 g of ammonia water (21.83%) was continuously added over 45 min, and further aging was continued for 60 min. After the phosphor powder was separated from the resulting reaction solution by filtration, it was dried at 100 ° C. for 3 hours or more to obtain phosphor particles having a 20 nm SiO ₂ film on the phosphor surface.
Next, phosphor particles having a SiO ₂ film were filled in a BN crucible, heated to 300 ° C. at 10 ° C./min in an ammonia atmosphere, and kept at 300 ° C. for 3 hours for heat treatment. In this way, a phosphor powder containing phosphor particles that were provided with a heat-treated SiO ₂ film on the surface and that was also heat-treated was obtained.
The phosphor powder had an oxygen concentration of 3.74 wt% and an average particle size (D50) of 12.10 μm.

(Comparative Example 2)
In Comparative Example 2, a phosphor powder containing the phosphor particles was obtained by performing the same treatment as in Example 2 except that the phosphor particles and the SiO ₂ film formed thereon were not subjected to heat treatment. A 20 nm SiO ₂ film was formed on the surface of the phosphor particles, but heat treatment in ammonia was not performed. The phosphor powder thus produced had an oxygen concentration of 3.87 wt% and an average particle size (D50) of 12.18 μm.

(Comparative Example 3)
In Comparative Example 3, phosphor particles were obtained by the same treatment as in Example 1 except that the surface of the phosphor powder was not provided with an SiO ₂ film and was not subjected to heat treatment. The obtained phosphor powder containing phosphor particles had an oxygen concentration of 3.34 wt% and an average particle diameter (D50) of 12.11 μm.

(Comparative Example 4)
In Comparative Example 4, to produce a phosphor particle to the composition without the addition of Al from the composition of Example 1, subjected to a heat treatment to provide a SiO ₂ film on the manufactured phosphor particle surface, SiO ₂ film is provided, The phosphor particles themselves were also heat treated. As manufacturing methods, commercially available SrCO ₃ (3N) and Si ₃ N ₄ (3N) are prepared as raw materials for M element and B element, respectively, and Eu ₂ O ₃ (3N) is prepared as Z element. . In these raw materials, the mixing ratio of each raw material was 0.970 mol for SrCO ₃ and 2.70 / 3 for Si ₃ N _{4 so} that the molar ratio of each element was Sr: Si: Eu = 0.970: 2.70: 0.030. mol, Eu ₂ O ₃ was weighed 0.030 / 2 mol, and mixed in the atmosphere using a rotating ball mill. Put the mixed raw materials in a BN crucible, raise the temperature to 1600 ° C at 15 ° C / min in a nitrogen atmosphere (flow state) at 0.05 MPa, hold and fire at 1600 ° C for 6 hours, and then from 1600 ° C to 200 ° C Cooled in 1 hour. After that, the fired sample is mixed and pulverized in the air, and the mixed and crushed sample is put again in the crucible, and the temperature is increased to 1750 ° C at a furnace pressure of 0.05 MPa at 15 ° C / min in a nitrogen atmosphere (flow state). After heating and holding at 1750 ° C. for 12 hours and main firing, it was cooled from 1750 ° C. to 200 ° C. in 1 hour. Thereafter, the fired sample was mixed and pulverized using a mortar until the particle size became an appropriate particle size in the air to obtain target phosphor particles.

30 g of the phosphor powder containing the phosphor particles is put into a mixed solvent of 500 g of isopropyl alcohol and 99.7 g of pure water, and the film temperature becomes 5.0 nm while maintaining the liquid temperature at 40 ° C. and continuing stirring. As described above, 0.867 g of tetraethoxysilane (TEOS, 95%) obtained from Formula 5 was added. After the addition of TEOS, 178.8 g of ammonia water (21.83%) was continuously added over 45 min using a tube pump, and further aging was continued for 60 min. After separating the phosphor powder from the obtained reaction solution by filtration, the phosphor powder was dried at 100 ° C. for 3 hours or more to obtain a phosphor powder containing phosphor particles having a SiO ₂ film.

Next, phosphor powder containing phosphor particles coated with SiO ₂ was filled in a BN crucible, heated to 300 ° C. at 10 ° C./min in an ammonia atmosphere, and heated at 300 ° C. for 3 hours. In this way, a phosphor powder containing phosphor particles that were provided with a heat-treated SiO ₂ coating on the surface and that had been heat-treated was also obtained. The obtained phosphor powder had an oxygen concentration of 3.93 wt% and an average particle size (D50) of 10.22 μm.

(Comparative Example 5)
In Comparative Example 5, a phosphor powder containing phosphor particles having a SiO ₂ film was obtained by performing the same treatment as in Comparative Example 4 except that the phosphor particles and their SiO ₂ film were not heat-treated. The obtained phosphor powder had an oxygen concentration of 4.00 wt% and an average particle size (D50) of 10.29 μm.

(Comparative Example 6)
In Comparative Example 6, a phosphor powder was obtained by performing the same treatment as in Comparative Example 4 except that the surface of the phosphor particles was not provided with an SiO ₂ film and heat treatment was not performed. The obtained phosphor powder had an oxygen concentration of 3.63 wt% and an average particle size (D50) of 10.16 μm.

(Evaluation)
Table 1 shows the phosphor powders according to Examples 1 and 2 and Comparative Examples 1 to 6 when excited with excitation light having an average particle diameter (D50), oxygen concentration (wt%), and a wavelength of 460 nm at 25 ° C. Luminescence characteristics (peak wavelength (nm), relative emission intensity when the emission intensity of the phosphor according to Comparative Example 3 is normalized to 100, and luminance when the intensity of the phosphor according to Comparative Example 3 is normalized to 100% , Chromaticity (x, y)), when the phosphor is heated to 300 ° C. and the emission intensity at the heating time of 0 min is normalized to 100, the heating time from 0 min (0 hour) to 360 min (6 hours) ) Shows the relative luminescence intensity after the lapse and its rate of change ((BP-AP) / BP).

In addition, the thermal deterioration measurement by heating of the phosphor was performed as follows.
First, the phosphor sample to be measured was excited with light having a wavelength of 460 nm at 25 ° C., and the emission intensity (BP) was measured. Next, 1.0 g of the phosphor powder for measurement was weighed, put into a crucible, and heated in the atmosphere at 300 ° C. for 6 hours using a muffle furnace to obtain a sample after thermal degradation. The sample after thermal degradation was excited with light at a wavelength of 460 nm at 25 ° C., and the emission intensity (AP) was measured. The rate of change in emission intensity due to thermal degradation ((BP-AP) / BP) Calculated.

The average particle diameters of the phosphor powders according to Examples 1 and 2 and Comparative Examples 1 to 3 are almost equal, and the phosphor particles are aggregated and sintered by providing a heat-treated SiO ₂ film. It can be seen that this does not occur. This is because the processing conditions of the phosphor powder according to Example 1 were set to the conditions for suppressing the reaction rate of SiO ₂ coating, and the heat treatment conditions were set to a temperature range (200 ° C. at which phosphor particles did not sinter). To 1000 ° C). The phosphor particle diameters of Comparative Examples 4 and 5 are considered to be approximately the same as the phosphor particle diameter of Comparative Example 6 due to the same effect.

It is considered that the oxygen concentrations of the phosphor powders according to Examples 1 and 2 and Comparative Examples 1 and ₂ are increased by applying the SiO ₂ film to the phosphor particle surfaces. Therefore, when the oxygen concentration of the phosphor powder according to Examples 1 and 2 and Comparative Examples 1 and 2 is compared with the oxygen concentration of the phosphor powder according to Comparative Example 3, the phosphor powder is coated with the SiO ₂ film. It turns out that the oxygen concentration of the body is rising. In addition, in Examples 1 and 2 and Comparative Examples 1 and 2, the emission intensity is maintained or slightly increased as compared with Comparative Example 3. This is because an oxide film is formed on the phosphor surface, and heat treatment is performed on the phosphor and its oxide film, so that oxygen diffuses from the oxide film to the phosphor, and the phosphor composition is made uniform by this oxygen diffusion. Is thought to have happened.

  In Example 1 and Comparative Example 1, and in Example 2 and Comparative Example 2, the thickness of the coated oxide film is different, but the effect on durability is not changed. However, if the film thickness is excessively large, the light emission characteristics of the phosphor are deteriorated. Therefore, the thickness of the oxide film is preferably 100 nm or less, more preferably 20 nm or less.

  Next, the results of heating the phosphor powders according to Examples 1 and 2 and Comparative Examples 1 to 3 in the air and evaluating the oxidation resistance will be described. As can be seen from the results in Table 1, the phosphors according to Examples 1 and 2 and Comparative Examples 1 and 2 have a rate of change ((( When evaluated by the value of (BP-AP) / BP), the decrease in emission intensity can be suppressed by 10% or more. Therefore, even if there is a heat treatment step of about 60 minutes in the commercialization process of various lighting devices using the phosphor according to the present invention, if the phosphor subjected to the process according to the present invention is used, it is commercialized. It has been found that it is possible to avoid a decrease in light emission characteristics in the process.

  Next, the same evaluation as described above was performed on the phosphor powder not containing Al in the phosphor particles according to Comparative Examples 4 to 6. As can be seen from the results in Table 1, the phosphors according to Comparative Examples 4 and 5 are compared to the phosphor according to Comparative Example 6 in terms of the rate of change with respect to thermal degradation ((BP-AP) / BP). As a result, the decrease in emission intensity can be suppressed by 10% or more. This is considered to be due to the effect of covering the surface with an oxide film. However, the phosphor powder containing no Al according to Comparative Examples 4 to 6 causes a decrease in emission intensity in the emission characteristics as compared with the phosphor powder containing Al in Examples 1 and 2. This is because, in the phosphor powder not containing Al according to Comparative Examples 4 to 6, when oxygen diffuses from the oxide film in the phosphor particles, the phosphor particles do not contain Al. This is thought to be due to the non-uniformity of light emission and the deterioration of the light emission characteristics.

(Example 5)
A blue light emitting element (emission wavelength: 460.0 nm) having a nitride semiconductor as a light emitting part was prepared, and the phosphor powder obtained in Example 1 and a commercially available yellow phosphor (YAG: Ce) was applied to produce a white LED, and the blue light emitting element was caused to emit light. At this time, a mixture of the emission spectrum of the blue light-emitting element, the yellow phosphor (YAG: Ce), and the emission spectrum of the phosphor according to Example 1 is simulated, and a light bulb color corresponding to a color temperature of 3000 K is calculated from the simulation result. The formulation was determined so that FIG. 1 shows an emission spectrum when the white LED emits light. FIG. 1 is a graph of a simulation result in which the horizontal axis represents the wavelength of light (nm) and the vertical axis represents the emission intensity. As is clear from the results in FIG. 1, each phosphor in the white LED was excited by light from the blue light emitting element to emit light, and white light having a color temperature of 3016K could be obtained. Moreover, the average color rendering index (Ra) of the white light was 91, R9 was 67, and R15 was 91, which was sufficiently excellent in color rendering. Furthermore, white LEDs having different correlated color temperatures could be obtained by changing the composition of the phosphor according to Example 1 and the yellow phosphor.

10 is a graph showing an emission spectrum of a white LED according to Example 5.

Claims (10)

A phosphor including phosphor particles having a surface formed with a heat-treated film made of SiO ₂ ,
The composition formula of the phosphor particles is represented by a general formula MmAaBbOoNn: Z (M element is one or more elements including Sr selected from Mg, Ca, Sr, Ba, and A element is Al, Ga) One or more elements including Al selected, B element is one or more elements including Si selected from Si and Ge, O is oxygen, N is nitrogen, and Z element is Eu) and 2.5 ≦ (a + b) / m <4.5, 0 <a / m <0.5, 2.0 <b / m <4.0, 0 ≦ o / m < 1.0, o <n, and n = 2 / 3m + a + 4 / 3b-2 / 3o. The phosphor according to claim 1,
The phosphor having a film thickness of 0.5 nm or more and 100 nm or less. The phosphor according to claim 1 or 2 ,
A phosphor according to the general formula, wherein 2.5 <(a + b) / m <4.0, 2.5 ≦ b / m ≦ 3.5, and 0 <o / m <1.0. The phosphor according to any one of claims 1 to 3 ,
A phosphor containing 0.1 wt% or more and 10.0 wt% or less of oxygen and 20.0 wt% or more and 50.0 wt% or less of nitrogen in the phosphor. The phosphor according to any one of claims 1 to 4 ,
The relative intensity value of the maximum peak in the emission spectrum at 25 ° C. when irradiating the phosphor with predetermined excitation light in the wavelength range of 250 nm to 500 nm is BP,
When the phosphor is placed in an atmosphere of 300 ° C. for 6 hours, then returned to 25 ° C., and the value of the relative intensity of the maximum peak in the emission spectrum when irradiated with the excitation light is AP,
A phosphor characterized in that (BP-AP) /BP≦0.05. The phosphor according to any one of claims 1 to 5 ,
The phosphor having an average particle diameter (D50) of 1.0 μm or more and 20 μm or less. A method for producing the phosphor according to any one of claims 1 to 6 ,
A step of firing phosphor materials to obtain phosphor particles;
Crushing the phosphor particles;
In a water-soluble organic solvent, the pulverized phosphor particles, the organosilane compound, and water are added and mixed, and then a gelling agent is added to form a film containing a metal oxide on the surface. Obtaining phosphor particles having,
Phosphor particles having a coating containing the metal oxide on the surface thereof are heat-treated in an atmosphere of ammonia gas and / or nitrogen gas at 1000 ° C. or lower and 200 ° C. or higher to obtain a heat-treated coating containing the metal oxide. And a step of manufacturing the phosphor particles. A light emitting device comprising the phosphor according to claim 1 and a light emitting unit. The light-emitting device according to claim 8 ,
The light emitting unit emits light in a wavelength range of 250 nm to 500 nm. The light-emitting device according to claim 8 or 9 ,
An LED (light emitting diode) is used as the light emitting portion.

Images